Apparatus and method for disintegrating the production pipe in the borehole

ABSTRACT

The apparatus for removing the production pipe (10) in the borehole is mechanically connected by means of BHA to an electrical power supply (12), coolant supply (13), data cable (14) and control unit (15). The equipment (X) is placed in a contactless manner inside the production pipe (10) and comprises a liquid precursor supply (11) which enters the generator (5) of the plasma-forming medium connected to the nozzle system inlet (6) connected to the nozzle system (7). The nozzle system (7) is placed in the space between two cylindrical mechanically movable electrodes, the upper electrode (1) and the lower electrode (2), and the upper electrode (1) and the lower electrode (2) are placed axially with respect to each other around the circumference of the equipment (X) and coaxially placed towards the production pipe (10), while in the axis of the upper electrode (1) and the lower electrode (2) there is around the nozzle system inlet (6) at least one magnet (4) placed above the nozzle system (7) and/or under the nozzle system (7). The method of removing the production pipe in the borehole by means of the equipment) (X) is carried out in such a way that the equipment (X) is inserted into the production pipe (10) in the borehole, and into the equipment (X) liquid precursor (Y) is supplied through the liquid precursor inlet (11) which enters the plasma-forming medium generator (5), which changes it to the plasma-forming medium (Z), which passes through the nozzle system inlet (6) into the nozzle system (7) and is injected from the nozzle system (7) into the space between two cylindrical mechanically movable electrodes, the upper electrode (1) and the lower electrode (2) where under the effect of the pressure in a range of 0.1-70 MPa and temperature of the plasma-forming medium (Z) in a range of 1-1000° C. the electric arc (3) is ignited in a liquid environment between the upper electrode (1) and the lower electrode (2).

FIELD OF TECHNOLOGY

The invention relates to equipment for removing a production pipe in theborehole and a method for removing the production pipe in the borehole.

STATE OF THE ART

Thousands of boreholes for the crude oil and natural extraction gasbuilt in the 20^(th) century are on the brink of their lifetime.Nowadays, due to the lack of profitability of extraction from theseboreholes, their temporary closure or even complete shutdown isconsidered. It is estimated that approximately 30,000 boreholes aroundthe world will have to be closed over the next fifteen years.“Decommissioning” is a term used to disable the installation/platform(which is the construction from which extraction is being carried out)from operation, which requires safe sealing of the hole on the earth'ssurface and the disposal of equipment used for offshore oil extraction.Decommissioning is a rapidly evolving market sector in the petroleumindustry, which has great potential for development but also carriesgreat risks. The decommissioning process needs to be well understood ifit needs to be managed with efficient spending of funds.

The most expensive decommissioning operation is Plug & Abandonment.

Plug & Abandonment (hereinafter only P & A) is the closure and permanentinsulation of the borehole. There are legislative and regulatoryrequirements associated with the P & A process, with the aim to ensuresufficient isolation and of the entire borehole against leakage offluids as well as for the protection of drinking water sources againsthydrocarbon contamination. In most cases of P & A, a series of cementplugs/seals is placed in the borehole, with a test to confirm theisolation function of these cement plugs at each level.

P & A consists of several steps: removing the production pipe from theborehole, from filling/sealing of the borehole, and finally removing theinfrastructure above the earth's surface, or on the bottom of the sea.

The task of P & A is to create a barrier to prevent leakage ofhydrocarbons to the earth's surface. The height of such a barrier isgiven by local legislation, for example, in the British North Sea, atleast 100 feet (approx. 30 meters) of the continuous layer of concreteimpeding the axial and radial flow of hydrocarbons is stated as usualrequirement in practice. Hydrocarbons could escape to the earth'ssurface along the original sheeting, respectively concrete. Therefore,it is necessary to precisely carry out the shutdown of the borehole. Theborehole closure consists, using conventional mechanical methods, of thefollowing steps:

-   -   Preparatory work and installation of the necessary        infrastructure,    -   Removing the “production tree” and installation of a “blowout        preventer” (BOP),    -   Cutting and removing the production pipe,    -   Milling of certain section of the steel sheeting of the        borehole,    -   Milling of concrete that separates the sheeting and rock massif,    -   Inserting the plug into the given section of the borehole,    -   And finally, the injection of new concrete closing the given        section of the borehole.

Blowout preventer (hereinafter only BOP) is a large valve at the top ofthe borehole which closes if the operators of the borehole lose controlover the borehole pressure. By closing this valve (usually controlledremotely by hydraulic drives), drilling operators gain control over theborehole, and then procedures for increasing the density of the mud canbe applied, until it is possible to open the BOP and maintain controlover the borehole pressure.

BOP is of critical importance for the safety of the operators of thedrilling rig, drilling accessories and the borehole itself.

In practice, the term “production tree” is used, which is the name for aset of valves, spools and fittings connected with the top part of theborehole to operate and control the flow of fluids originating in theborehole. Production tree is used only during production, not usedduring drilling.

The most time-consuming step in the decommissioning process areinitiating operations, i.e. installing the necessary infrastructure,removing the production tree and installing the BOP, removing theproduction pipe and milling the sheeting. These operations bring themost potential complications.

Steel sheeting and concrete don't need to be milled in the case if theconcrete which separates sheeting and rock massif is of sufficientquality. This quality is mainly determined by conventional ultrasonicmethods known as “cement bond log”. A “cement bond log” (hereinafteronly CBL) is the term used for a system in which acoustic logs provide ameans of assessing the mechanical integrity and quality of the cementbond. Acoustic logs measure the quality of the cement directly, wherebythis value derives from the degree of acoustic bond of cement tosheeting and rock. Correctly made and interpreted cement bond logs (CBL)provide highly reliable estimates of the borehole integrity andisolation of the individual zones.

Since these methods cannot analyze cement through two layers of steelmaterial, in conventional methods it is necessary to cut off theproduction pipe and remove it from the borehole. This operation usuallytakes a few days and requires the presence of a conventional drillingrig with sufficient capacity to pull out the production pipe (which maybe several kilometres long).

A different technical problem is solved by the borehole closureprocedure which is called Perforate & Wash & Cement (PWC), in which itdoes not come to removing the production pipe from the borehole but onlyto its perforation. The formed holes cannot be used to verify the cementquality by CBL method, which is a considerable disadvantage. The PWCmethod is also subsequently associated with other disadvantages, such asuneven cement distribution during the cementation process and thusinsufficient isolation, which can lead even to leakage of hydrocarbons.

P & A costs are costs without turnover generation. Naturally, miningcompanies around the world are looking for effective solutions to helpreduce these massive expenses.

Research and development in the mining segment focused primarily onprogressive materials and methods in the field of drilling and assemblyof the borehole, while the development of innovative technologies in theP & A field has long been neglected.

Up to now, particularly conventional mechanical technologies have beenused in the P & A field.

A conventional method based on the use of a hydraulically operatedtool—milling cutter, is currently being developed by the company DeltideEnergy Services, LLC in the document WO2016085899 A1. It is a mechanicalmilling tool (called Medusa), which, in addition to the standard axialmovement, is able to change its position even in the radial direction,thus achieving removing material also from misaligned production pipes.

Similarly, in the document AU2014280087 of the company Welltec A/S atool is described that can adapt the position of blades to productionpipe geometry, i.e. radially press the blades and anchoring arms whichensure stabilisation.

The disadvantages of conventional mechanical methods are in particular:

-   -   1) The need for a heavy rotary drilling rig to pull out the        production pipe, while renting the rig is costly,    -   2) Damage and locking of the tool may occur, or seizing some of        its part in the borehole during cutting of the production pipe,    -   3) Demanding and costly processing and recycling of the        production pipeline, which, moreover, often shows low levels of        radioactivity caused by long-term placement in the borehole.

In order to eliminate the disadvantages of conventional mechanicalmethods, conventional methods are increasingly combined withunconventional ones, such as in the patent application WO2016170048 ofthe company Welltec A/S. The invention uses conventional mechanicalmilling technology enhanced by the addition of a corrosive additivewhich weakens and etches off the wall of the production pipe in theborehole. The milling blades then remove the thinned wall, i.e. themilling cutter takes less material from the production pipe.

Also, the company Spex Engineering Ltd. deals with the development of analternative method based on a controlled explosion. In the documentsGB2532609A, GB2533844A and US2016290082A1, the idea of using adetonation mechanism to remove borehole materials is developed. The useof carrier materials allows the generation of thermal energy and theexpansion of gases directed to a concrete place of degradation of thematerial. The type of explosive material used in the equipmentdetermines the interaction zone and at the same time the amount andplacement of the required segments.

The document GB2532609A discloses in more detail fuels into rocketmotors as carrier/explosive material that provide detonation and thenecessary heat and kinetic energy to remove materials. The presence ofoxygen improves the detonation mechanism. The main used mechanism is thecombustion process and the subsequent detonation.

The company Interwell Technology AS deals with an alternative based onexothermic chemical reactions, e.g. explosion, e.g. in the documentWO2013135583A2. The mechanism of removing the production pipe is themelting of the material using the heat-generating mixture of thermite.The process runs spontaneously, it cannot be controlled afterinitialization. The borehole is permanently closed by solidification ofthe melt.

The technology of exothermic chemical reactions is also used in the“Radial Cutting Torch” technology. A typical example of this technologyis the U.S. Pat. No. 6,598,679 B2. It describes a technology thatperforates the production pipe around the circumference and divides itinto two parts.

The technology is based on combustible/fuel pellets that are built intothe cylindrical body of the cutter. After an electrical ignition ofcombustible/fuel, the hot liquid environment expands, and a high-speedand high-temperature flow is generated through the outflow nozzlesplaced in one plane around the circumference.

The aforementioned technology is used for cutting, and it is a processthat is only performed once (as the amount of explosive in the cutterbody is limited). It is not a continuous process.

Another alternative direction to the conventional method of mechanicalmilling is the use of a laser described e.g. in the patent AU2015203686of the company Halliburton Energy Services Inc. The laser beam that isfed into the space can be directed to the selected position andpositioned in the immediate vicinity. In the set position, the laserbeam gradually cuts the production pipe material and sheeting up to therock material.

Disadvantages of Alternative Technologies:

Technologies Problem Explosive The complexity of repeating the processLarger splinters/chips may be created (explosive cutting of the companySpex) Laser Transfer of signal energy over long distances Attenuation ofthe signal Impurities/defects in the optical fibre that are heatedduring signal transfer The complexity of repeating the process

The size or unsuitable shape of splinters complicates the “milling”process”, most often with conventional mechanical technologies, butlarger splinters can also occur with some combined alternativetechnologies (e.g. explosive cutting of the company Spex).

The most promising alternative direction to the conventional method ofmechanical milling is a technology based on the use of plasma.

The technology of plasma cutting of metallic materials under atmosphericconditions is made by the so-called plasma cutter.

With this cutting method, the plasma flow is concentrated to a smallcross-section (at the level of mm² units). This the most strikingshortcoming of such equipment, since it is a point effect rather than aplanar one.

Plasma cutters use a flow of gaseous media for their activity, thusbeing dependent on the physicochemical properties of this medium.

For high-pressure gaseous medium, based on the present knowledge, it isnot technically possible to ensure sufficient energy flow density forthe plasma cutter. The reason is voltage limitations of the sources, thedesign electrical isolation limits and constraints given for the purposeof use in the borehole environment.

Moreover, in the case of supercritical phase transformation of themedium, associated with the increase in ambient pressure, theseproperties change abruptly, making it impossible to use the plasmacutting principle for this environment.

The basis of milling technology with using plasma is described in thedocument WO2014137299 A1 of the company GA Drilling, a.s., where the useof plasma for thermal removal of conductive and non-conductivematerials, preferably in the axial direction, is generally described.The equipment uses helically rotating electric arc drawn from thecentral electrode to the surface of the outer electrode. The describedsolution requires the creation of a relatively long electric arc withsufficient thermal action at atmospheric pressure realizable atatmospheric pressure. However, the existence of a helically rotatingelectric arc with a given geometry of the equipment at pressures higherthan atmospheric, as well as the actual realization of the materialremoval process using current technology and knowledge is veryproblematic, or questionable, since in higher pressures at the sourcewith the same parameters, the maximum sustainable length of the electricarc significantly decreases, what is also related to the reach of theprocess.

The optimization of the metal removing technology is described in thepatent application WO2016105279 of the company GA Drilling, a.s., wherethe material removal efficiency is increased by elongation of the arc(thus increasing electrical and thus thermal power) by the principle ofthe arched connection, i.e. the localization of the heat output, wherethe arc burns between the electrode and the metal pipeline removed. Sucha mode, however, requires a high-quality electrical connection of thesource pole with the metal pipeline removed. The disadvantage of such asolution is also the considerably higher voltage requirements tomaintain the bonded (long) arc in the liquid environment at increasedpressures which limit its usability in the borehole environment.

SUMMARY OF THE INVENTION

The requirement of the drilling industry is currently a technology thatwould eliminate the shortcomings of the present technical solutions inthe field of the production pipe removing, i.e. a technology that doesnot require a production pipe to be taken out from the borehole, and forits operation a simple, easy and thus cheap drilling kit can be used.

Modern drilling technology involves the use of “coiled tubing” insteadof conventional rotating drill pipes. The advantage is that the coiledtubing offers simpler processes of commissioning and pulling out fromthe borehole compared to the drill pipes which must be connected andlater dismantled during the process of commissioning and pulling out.

Another advantage is that the coiled tubing enters the borehole througha “stripper”, mounted under the “injector head”. Stripper is equipmentwhich ensures the primarily operational sealing between pressurizedfluids in the borehole and the surface environment, and thus providesdynamic sealing around the “coiled tubing” during operation. By this, itoffers borehole control capabilities beyond those that are possible withconventional drilling pipeline, and thus allows also drilling so-called“underbalanced boreholes”, where the pressure is less than optimal.

The injector head provides a driving force for inserting and removingcoiled tubing from the borehole. An important advantage of coiled tubingis the significantly lower cost of purchasing or renting in comparisonwith a conventional rotary drilling rig.

The solution of the present invention eliminates the shortcomings of thesolutions known up to now. For the needs of describing the invention andthe unambiguous definition of the equipment orientation in theproduction pipe we state, that the equipment is connected to anelectrical power supply, a coolant supply, a liquid precursor supply,data cable and control unit, which are connected to the equipment on thetop side of the equipment (i.e. from the side of the borehole surface).

The invention relates to equipment for removing a production pipe in theborehole and a method for removing the production pipe in the borehole.

The equipment can also be classified as a milling head that is part ofthe “Bottom Hole Assembly” (hereinafter only BHA). BHA is that part ofthe drilling rig that runs into the borehole and allows adjusting thenecessary inputs for the milling head directly above the milling point.

The invention addresses the removal of the production pipe by means ofan electric arc nozzle rotating in a liquid environment in the presenceof a plasma-forming medium, preferably a mixture of supercritical waterand supercritical oxygen. Removing the production pipe is made withoutdirect contact of the equipment with the pipeline, which results inelimination of undesirable degradation of the material of the millingtools and elimination of the necessity to exchange the milling toolsduring the process of removing the production pipe.

The equipment can make a hole in the production pipeline, through whichCBL measurement can be made.

The advantage of such a solution is that it is not necessary to take outa multi-kilometre production pipe, and in addition to saving costs, alsoelimination of health risks due to the contact of the operators with theproduction pipe is not negligible.

The equipment for removing the production pipe in the borehole is placedin a contactless manner inside the production pipe and comprises aliquid presursor supply which enters the plasma-forming mediumgenerator, and the plasma-forming medium generator is connected to thenozzle system inlet connected to the nozzle system, while the nozzlesystem is placed in the space between two cylindrical mechanicallymovable electrodes, an upper electrode and a lower electrode. The upperelectrode and the lower electrode are placed axially with respect toeach other around the circumference of the equipment and are coaxiallyplaced towards the production pipe. Both electrodes are connected to astandard motion mechanism that allows independent movement ofelectrodes. In the axis of electrodes, around the nozzle system inletthere is at least one magnet placed. The magnet may be placed below thenozzle system, above the nozzle system, or simultaneously under as wellas above the nozzle system. The magnet is a permanent magnet orelectromagnet.

The equipment is inserted into the production pipe in the borehole,whereby its diameter is in the cross-section adjusted to thecross-section of the production pipe so that there is free space betweenthe equipment and the production pipe and the equipment does not touchthe production pipe. Thus, the equipment is placed in the productionpipe in a contactless manner, but in the case of a large length of theequipment, one or more centralizers are placed on the equipment, whichare in a mechanical contact with the production pipe.

The equipment is mechanically connected with the remaining part of theBHA and is in a standard manner connected by means of interconnectionunits with the electrical power supply, coolant supply, liquid precursorsupply, data cable and control unit.

The plasma-forming medium generator consists of at least one chamber, orseveral interconnected chambers, each chamber having at least one inletand one outlet. In the case of multiple chambers, these are arranged inseries, in parallel or in a combination of these methods. There arethree possibilities of content of chamber, namely:

-   -   A catalyst    -   Or at least one pair of electrodes, the first electrode being at        a negative electrical potential and the second electrode being        at a positive electrical potential    -   Or the resistance wire or the chamber is surrounded by the        resistance wire.

A preferred solution is, if at least one generator chamber contains atleast one pair of electrodes, the first electrode being at a negativeelectrical potential and the second electrode being at a positiveelectrical potential.

The nozzle system is composed of 3 to 150 channels placed radiallytowards the production pipe or at an angle of 1-90° from the radialdirection.

An upper dynamic flow restrictor may be placed on the outside of theequipment, between the equipment and the production pipe, at least 10 mmabove the level of the nozzle system and/or a lower dynamic flowrestrictor may be placed on the outside of the equipment, between theequipment and the production pipe, at least 10 mm under the level of thenozzle system.

The use of restrictors in the equipment is not necessary, but has thefollowing benefits for the breakdown process:

Upper dynamic flow restrictor

-   -   Prevents leakage of superheated plasma-forming medium which        desirably preheats the production tube to a higher initiation        temperature,    -   Prevents flushing of chips into the space between the equipment        and the production pipe,    -   Prevents the penetration of the surrounding drilling fluid        (water, brine, mud . . . ) into the process,    -   By maintaining the plasma-forming medium with the lower density        in the process area, the radial reach of the process increases.

Lower dynamic flow restrictor

-   -   Prevents leakage of superheated plasma-forming medium which        desirably preheats the production tube to a higher initiation        temperature,    -   Prevents the penetration of the surrounding drilling fluid        (water, brine, mud . . . ) into the process,    -   By maintaining the plasma-forming medium with the lower density        in the process area, the radial reach of the process increases,    -   Directs the flow of the superheated plasma-forming medium        towards the production pipe.

An electromagnet (M) may be placed at the bottom of the equipment, thepurpose of which is to collect the chips formed during the productionpipe removing process.

The equipment operates in a wide range of pressures of 0.1 MPa-70 MPa.An advantage is the continuous operation of the equipment without theneed for exchange/modification of the components at different depths ofthe borehole.

The process of removing the production pipe in the borehole with theaction of the equipment described above begins by inserting theequipment into the production pipe without contact with the productionpipe.

Subsequently, a liquid precursor is introduced into the equipment viathe liquid presursor supply. The liquid precursor is a mixture ofethanol and water in any ratio, or a mixture of hydrogen peroxide andwater in any ratio, water or an aqueous alkali metal hydroxide solutionwith a concentration of 0.01-5% by weight.

The plasma-forming medium generator modifies the incoming liquidprecursor to plasma-forming medium by thermal, electrochemical orchemical decomposition, or a combination of at least two of thesedecompositions—depending on the type of equipment, and additional energymay be released.

The plasma-forming medium has the following properties:

-   -   For pressures from 0.1 to 5.03 MPa: waters enriched with oxygen,        or mixtures of water vapour and oxygen,    -   For pressures from 5.04 to 22.05 MPa: mixtures of water and        supercritical oxygen, or mixtures of water vapour and        supercritical oxygen,    -   For higher pressures from 22.06 to 70 MPa (with temperature        374-1000° C.): mixtures of supercritical water and supercritical        oxygen (SCW+SCO).

After its formation, the plasma-forming medium passes through the nozzlesystem inlet into the nozzle system and is injected from the nozzlesystem into the inter-electrode space under the effect of the ambientpressure in a range of 0.1-70 MPa. The temperature of the plasma-formingmedium is in the range of 1-1000° C.

The used plasma-forming medium has the following advantages for theprocess:

-   -   Expansion in the transformation of the liquid precursor to the        plasma-forming medium—increasing the range of the process        effect,    -   Creates better conditions for arc initiation and stability        (low-energy process),    -   Higher degree of oxidation of the removed material.

The main role of the plasma-forming medium is to ensure suitableconditions for the creation and existence of plasma for plasma removalof materials/milling. Increased oxygen concentration in theplasma-forming medium favours the degradation process, and additionalthermal energy is released. A part of the released additional energy isconsumed to increase the thermodynamic temperature of the plasma-formingmedium passing through the electric arc, where the temperature of themedium incident to the surface of the production pipe material isfurther increased; the remaining part of the energy is consumed by thevolume expansion of the decomposed medium. Higher thermodynamictemperature accelerates the process of oxidation and overall degradationof the production pipe material. The expansion increases the distance inthe radial direction, to which the equipment is capable ofdisintegrating the production pipe material, and at the same time theefficiency of removing the broken production pipe material increases byexpansion.

The plasma-forming medium has 3 decisive properties with respect toelectric parameters and the electric arc stability:

-   -   Low permissivity—the lower permissivity, the lower arc voltage        requirements,    -   Low density—the lower density, the lower arc voltage        requirements; at lower density it is easier to move the medium        and this exhibits smaller voltage and shape fluctuations,    -   Above the critical point of water, the presence of the arc does        not trigger further phase change, and therefore it is more        energy efficient to maintain the electric arc.

Prior to starting the P & A process, in many cases, a borehole is filledwith a fluid such as brine or seawater in which residual hydrocarbons orresidues of fluid used in drilling (on an aqueous or oil basis) may bepresent.

The process continues by the subsequent ignition of the electric arc inthe fluid at high borehole pressure (up to 70 MPa) between the upperelectrode and the lower electrode which are placed coaxially with theproduction pipe. The arc is ignited either by contact ignition orvoltage ignition.

Contact ignition is accomplished by approaching, touching bothelectrodes and then separating them to the required distance (FIG. 1).

For voltage ignition, the advantage of mechanically movable electrodesis also fully used, and a fixed voltage value in the 0.1 kV-1 MV range,which is not pulse-like, is used to carry out the electricalbreakthrough. Electric arc ignition takes place at a constant electricvoltage, the inter-electrode distance begins to change and theelectrical breakthrough takes place after reaching the minimum distancerequired to form a conductive channel between both electrodes. In thiscase, the electrodes will not touch. After ignition the electric arc,the electrodes move away to the required distance.

The main purpose of using this method of initiating the electric arc isto ensure reliability and higher efficiency of the electric arc ignitionprocess in a wide range of pressures and in a fluid environment.

After ignition the electric arc, elongation of the arc channel to thelength from 0.1 to 20 mm occurs by deflecting the electrodes in theaxial direction. The electric arc is then maintained by a constantelectric current.

The inter-electrode distance is kept approximately constant throughoutthe entire milling time at a selected value in the range from 0.1 to 20mm.

The electric arc burns exclusively between a pair of electrodes of thesame shape and the length of the electric arc is adapted to theelectrical source parameters. The arc length detection is performed bycontinuous monitoring the required average voltage required to maintainthe electric arc. The electric arc input power is 10-10000 kW.

With the stated mode of maintaining the electric arc—unlike in oldersolutions—the electrode wear is more uniform, thereby simplifying thecontrol of the electrode movement.

The electric arc burns between two cylindrical electrodes in a liquidenvironment at an ambient pressure in the range from 0.1 to 70 MPa andis evenly rotated by a Lorentz force on a circle, the axis of therotational movement of the arc being identical to the axis of symmetryof the electrodes, thus eliminating the need to rotate the components ofthe equipment. In this case, the term rotated on a circle means themovement of the two roots of the electric arc on a circle.

The rotation of the electric arc is ensured by the magnetic field of apermanent magnet or electromagnet and/or by the interaction of theelectric arc with the flow of the plasma-forming medium.

Since the actual breakdown process does not require a mechanical contactof the broken material and equipment, mechanical wear of the functionalparts of the equipment does not occur and the efficiency of theequipment does not decrease over time. Additionally, the process alsooperates at a pressure range from 0.1 to 70 MPa, and therefore it is notnecessary to exchange the equipment during the milling process atvarious depths. The necessary wear of the electrodes, which occursduring the process, is compensated by an increase in the volume of thewear part, by the material composition itself and by the electrodeconstruction, as well as by the mutual axial movement of the electrodes.This ensures that it is not necessary to change the milling tool or itsparts during the entire time of the production pipe removing due to wearor different pressures of the surrounding environment.

The production pipe material is degraded by the heat flow produced bythe joint action of the rotating electric arc and the plasma-formingmedium, whereby the created heat flow has the character of a flataction.

The process of the production pipe breakdown involves severalsimultaneously acting mechanisms. The triggering element of eachmechanism is an elevated temperature.

The temperature triggers the first mechanism, which is the meltingprocess, which directly results in the mechanical separation of degradedmaterial in the form of melt from the production pipe. The secondmechanism of degradation is high-temperature oxidation, a directexothermic reaction of solid or melted material of the production pipewith oxygen, or another oxidizing agent supplied in the plasma-formingmedium.

Additional energy is supplied to the breakdown process by theplasma-forming medium flow from nozzles towards the wall of theproduction pipe, through inter-electrode space, where the medium passesthrough the electric arc. The radial flow component contributes to theefficient transfer of heat output to the disintegrated material of theproduction pipe.

Subsequently, the broken material of the production pipe is separatedfrom the production pipe and removed from the breakdown point. Thematerial is broken mainly to particles of a size 0.01-5 mm.

The degree of roughness of the remaining material of the production pipeafter milling does not exceed the size of the created particles.

The broken material of the production pipe is removed from the breakdownpoint by hydrodynamic force generated by the flow of the plasma-formingmedium, coolant and mud acting on the broken particles or thegravitational force.

Particles of broken material—chips:

1) Are flushed by mud to the surface, or

2) Are guided by the flow of media to the bottom of the borehole, orother closure of the borehole, or

3) Are trapped by electromagnet in the bottom part of the equipment,since the originated chips are magnetic. This provides for moreintensive removing chips from the breakdown point of the productionpipe, while at the same time ensuring the reduction of the chip trappingon the magnet responsible for the rotation of the electric arc, therebyprolonging its lifetime. After termination of the equipment action, theelectromagnet can be switched off and trapped chips fall into the bottomof the borehole.

The use of a particular type of chip removal depends on the requirementsof the borehole operator.

After the desired section of the production pipe is milled, the processof removing the production pipe in the borehole is terminated byextinguishing the arc. The equipment is subsequently pulled out of theborehole.

The equipment may be placed in the production pipe centrically as wellas eccentrically, to remove the unsymmetrical part of the productionpipeline.

DESCRIPTION OF FIGURES ON DRAWINGS

FIG. 1 presents the process of contact ignition.

FIG. 2 presents equipment for removing the production pipe with twomagnets, with upper and lower dynamic flow restrictor and electromagnetfor the chip trapping. It is positioned centrically in the productionpipe in a lateral cross-section, and in a cross-section from above.

FIG. 3 presents equipment for removing the production pipe with onemagnet, without dynamic flow restrictors and without electromagnet forthe chip trapping. It is positioned centrically in the production pipein a lateral cross-section.

FIG. 4 presents equipment for removing the production pipe with twomagnets, without dynamic flow restrictors and without electromagnet forthe chip trapping. It is positioned eccentrically in the productionpipe, in a lateral cross-section and in a cross-section from above.

FIG. 5 presents equipment for removing the production pipe with onemagnet, with upper dynamic flow restrictor and with electromagnet forthe chip trapping. It is positioned centrically in the production pipein a lateral cross-section.

FIG. 6 presents equipment for removing the production pipe with onemagnet, with lower dynamic flow restrictor and without electromagnet forthe chip trapping. It is positioned centrically in the production pipein a lateral cross-section.

EXAMPLES OF EMBODIMENTS

The equipment X for removing the production pipe 10 in the borehole ismechanically connected by means of BHA to an electrical power supply 12,coolant supply 13, data cable 14 and control unit 15. The equipment X isplaced in a contactless manner inside the production pipe 10 andcomprises a liquid presursor supply 11 which enters the plasma-formingmedium generator 5 connected to the nozzle system inlet 6 connected tothe nozzle system 7, while the nozzle system 7 is placed in the spacebetween two cylindrical mechanically movable electrodes, an upperelectrode 1 and a lower electrode 2, and the upper electrode 1 and thelower electrode 2 are placed axially with respect to each other aroundthe circumference of the equipment X and coaxially placed towards theproduction pipe 10, while in the axis of the upper electrode 1 and thelower electrode 2 there is around the nozzle system inlet 6 at least onemagnet 4 placed above the nozzle system 7 and/or under the nozzle system7. The magnet 4 is a permanent magnet or electromagnet. Plasma-formingmedium generator 5 consists of one chamber 18, or several interconnectedchambers 18, each chamber 18 having at least one inlet and one outlet.In the case of multiple chambers 18, these are arranged in series, inparallel or in a combination of these methods. There are threepossibilities of content of chamber 18, namely:

-   -   A catalyst    -   Or at least one pair of electrodes, the first electrode 16 of        the generator being at a negative electrical potential and the        second electrode 17 of the generator being at a positive        electrical potential    -   Or the resistance wire or the chamber 18 is surrounded by the        resistance wire.

A preferred solution is, if at least one generator chamber 18 containsat least one pair of electrodes, the first electrode 16 being at anegative electrical potential and the second electrode 17 being at apositive electrical potential.

The nozzle system 7 is composed of 3 to 150 channels placed radiallytowards the production pipe 10 or at an angle of 1-90° from the radialdirection.

The equipment is in the production pipe 10 placed without contact withthe production pipe, but in the case of a longer equipment, one or morecentralizers C are placed on the outside of the equipment X, which arein mechanical contact with the production pipe 10.

An electromagnet M may be placed at the bottom of the equipment X.

The equipment X is placed in the production pipe 10 centrically, oreccentrically.

Between the equipment X and the production pipe 10, restrictors can beplaced, namely upper dynamic flow restrictor 8 and/or lower dynamic flowrestrictor 9.

The equipment X and all its parts are adapted to operate at a pressurein the range from 0.1 to 70 MPa.

The method of removing the production pipe in the borehole by means ofthe equipment X is carried out in such a way that the equipment X isinserted into the production pipe 10 in the borehole, and into theequipment X through the liquid precursor inlet 11 liquid precursor Y issupplied which enters the plasma-forming medium generator 5 and changesin it to the plasma-forming medium Z, which passes through the nozzlesystem inlet 6 into the nozzle system 7 and is injected from the nozzlesystem 7 into the space between the upper electrode 1 and the lowerelectrode 2 where under the effect of the pressure in a range of 0.1-70MPa and temperature of the plasma-forming medium Z in a range of 1-1000°C. the electric arc 3 is ignited, either by contact ignition or voltageignition, in a liquid environment between the upper electrode 1 and thelower electrode 2. The electric arc 3 is evenly rotated on a circle, theaxis of the rotational movement of the arc 3 being identical to the axisof symmetry of the upper electrode 1 and the lower electrode 2, and therotation of the electric arc 3 is ensured by the magnetic field of amagnet 4 and/or by the interaction of the electric arc 3 with the flowof the plasma-forming medium Z. The electric arc 3 input power is in arange of 10-10000 kW. The production pipe material 10 is degraded by theheat flow produced by the joint action of the rotating electric arc 3and the plasma-forming medium Z, subsequently the broken material isseparated from the production pipe 10 and is removed from the breakdownpoint, and then the electric arc 3 is extinguished and the equipment Xis pulled out from the production pipe 10 to the outside of theborehole.

The plasma-forming medium generator 5 modifies the liquid precursor Y tothe plasma-forming medium Z by thermal, electrochemical or chemicaldecomposition, or a combination of at least two of these decompositions.

For pressures from 22.06 to 70 MPa and temperatures from 374 to 1000°C., the plasma-forming medium Z has the properties of a mixture ofsupercritical water and supercritical oxygen, for pressures from 5.04 to22.05 MPa, the plasma-forming medium Z has the properties of a mixtureof water and supercritical oxygen, or a mixture of water vapour andsupercritical oxygen, and for pressures from 0.1 to 5.03 MPa, theplasma-forming medium Z has the properties of a mixture of water andoxygen (oxidizing agent), or a mixture of water vapour and oxygen.

The liquid precursor Y is water, a mixture of ethanol and water in anyratio, a mixture of hydrogen peroxide and water in any ratio, or anaqueous alkali metal hydroxide solution with a concentration of 0.01-5%by weight.

After ignition the electric arc 3 by deflecting the electrodes, of theupper electrode 1 and the lower electrode 2 elongation of the arcchannel to the length of 0.1 to 20 mm in the axial direction occurs.Inter-electrode distance between the upper electrode 1 and the lowerelectrode 2 is maintained at a constant value selected from an intervalof 0.1-20 mm after the electric arc 3 has been stabilized.

The particles of broken material of the production pipe 10 may betrapped by electromagnet M placed at the bottom of the equipment X.

The broken material of the production pipe 10 is removed from thebreakdown point by hydrodynamic force generated by the flow of theplasma-forming medium Z, coolant 13 and mud acting on the brokenparticles or the gravitational force.

Example 1

The equipment X has two magnets 4 and both magnets are permanentmagnets.

An upper dynamic flow restrictor 8 is placed on the outside of theequipment X, between the equipment and the production pipe 10, 10 mmabove the level of the nozzle system 7.

The nozzle system 7 is composed of 36 channels placed at an angle of 26°from the radial direction towards the production pipe.

At the bottom of the equipment X, an electromagnet M is placed.

The equipment X is placed in the production pipe 10 centrically.

The liquid precursor Y is aqueous hydrogen peroxide solution with aconcentration of 69% by weight.

It enters the plasma-forming medium generator 5 and changes in it byelectrochemical decomposition to the plasma-forming medium Z and thispasses through the nozzle system inlet 6 into the nozzle system 7.

Plasma-forming medium Z is injected from the nozzle system 7 into thespace between two cylindrical mechanically movable electrodes, the upperelectrode 1 and the lower electrode 2 under the effect of the ambientpressure of 30 MPa. Plasma-forming medium Z has a temperature of 400° C.and the properties of a mixture of supercritical water and supercriticaloxygen.

The electric arc 3 is ignited by voltage ignition in a liquidenvironment between the upper electrode 1 and the lower electrode 2.Inter-electrode distance between the upper electrode 1 and the lowerelectrode 2 is maintained at a constant value of 3 mm after the electricarc 3 has been stabilized.

The broken material of the production pipe 10 is removed from thebreakdown point by hydrodynamic force generated by the flow of theplasma-forming medium Z acting on the broken particles. Subsequently,the particles of broken material (chips) are trapped by electromagnet Mat the bottom of the equipment X.

After the end of the process, the electric arc 3 is extinguished,electromagnet M is switched off and trapped chips fall into the bottomof the borehole. Subsequently, the equipment is pulled out from theproduction pipe 10 to the outside of the borehole.

Example 2

The equipment X in FIG. 2 has two magnets 1, and both are permanentmagnets.

An upper dynamic flow restrictor 8 is placed on the outside of theequipment X, between the equipment and the production pipe 10, at least10 mm above the level of the nozzle system 7.

A lower dynamic flow restrictor 9 is placed on the outside of theequipment X, between the equipment and the production pipe 0 at least 10mm under the level of the nozzle system 7.

One centralizer C is placed on the outside of the equipment X, betweenthe equipment and the production pipe 10, which is in a mechanicalcontact with the production pipe 10.

The nozzle system 7 is composed of 24 channels placed radially towardsthe production pipe.

At the bottom of the equipment X, an electromagnet M is placed. Theequipment X is placed in the production pipe 10 centrically.

The liquid precursor Y is aqueous hydrogen peroxide solution with aconcentration of 35% by weight.

It enters the plasma-forming medium generator 5 and changes in it byelectrochemical decomposition to the plasma-forming medium Z and thispasses through the nozzle system inlet 6 into the nozzle system 7.

Plasma-forming medium Z is injected from the nozzle system 7 into thespace between two cylindrical electrodes, the upper electrode 1 and thelower electrode 2 under the effect of the ambient pressure of 19 MPa.Plasma-forming medium Z has a temperature of 200° C. and the propertiesof a mixture of water and supercritical oxygen.

The electric arc 3 is ignited by voltage ignition in a liquidenvironment between the upper electrode 1 and the lower electrode 2.Inter-electrode distance between the upper electrode 1 and the lowerelectrode 2 is maintained at a constant value of 10 mm after theelectric arc 3 has been stabilized.

The broken material of the production pipe 10 is removed from thebreakdown point by hydrodynamic force generated by the flow of theplasma-forming medium Z acting on the broken particles. Subsequently,the particles of broken material (chips) are trapped by electromagnet Mat the bottom of the equipment X.

After the end of the process, the electric arc 3 is extinguished,electromagnet M is switched off and trapped chips fall into the bottomof the borehole. Subsequently, the equipment is pulled out from theproduction pipe 10 to the outside of the borehole.

Example 3

The equipment X is long, and therefore it has two centralizers C placedon the outside of the equipment X between the equipment a productionpipe 10, which are in a mechanical contact with the production pipe 10.

The equipment X has two magnets 4 and both are permanent magnets.

A lower dynamic flow restrictor 9 is placed on the outside of theequipment X, between the equipment and the production pipe 10, 10 mmunder the level of the nozzle system 7.

The nozzle system 7 is composed of 8 channels placed at an angle of 60°from the radial direction towards the production pipe. The equipment Xis placed in the production pipe 10 centrically.

The liquid precursor Y is aqueous ethanol solution with a concentrationof 96% by weight.

It enters the plasma-forming medium generator 5 and changes in it byelectrochemical decomposition to the plasma-forming medium Z and thispasses through the nozzle system inlet 6 into the nozzle system 7.

Plasma-forming medium Z is injected from the nozzle system 7 into thespace between two cylindrical electrodes, the upper electrode 1 and thelower electrode 2 under the effect of the ambient pressure of 15 MPa.Plasma-forming medium Z has a temperature of 30° C. and the propertiesof a mixture of water and supercritical oxygen.

The electric arc 3 is ignited by contact ignition in a liquidenvironment between the upper electrode 1 and the lower electrode 2.Inter-electrode distance between the upper electrode 1 and the lowerelectrode 2 is maintained at a constant value of 7.5 mm after theelectric arc 3 has been stabilized.

Example 4

The equipment X in FIG. 4 has two magnets 4 and both are electromagnets.

The nozzle system 7 is composed of 120 channels placed at an angle of 5°from the radial direction towards the production pipe.

The equipment X is placed in the production pipe 10 eccentrically.

The liquid precursor Y is aqueous potassium hydroxide solution with aconcentration of 3% by weight.

It enters the plasma-forming medium generator 5 and changes in it byelectrochemical decomposition to the plasma-forming medium Z and thispasses through the nozzle system inlet 6 into the nozzle system 7.

Plasma-forming medium Z is injected from the nozzle system 7 into thespace between two cylindrical electrodes, the upper electrode 1 and thelower electrode 2 under the effect of the ambient pressure of 70 MPa.Plasma-forming medium Z has a temperature of 100° C. and the propertiesof a mixture of water and supercritical oxygen.

The electric arc 3 is ignited by voltage ignition in a liquidenvironment between the upper electrode 1 and the lower electrode 2.Inter-electrode distance between the upper electrode 1 and the lowerelectrode 2 is maintained at a constant value of 0.8 mm after theelectric arc 3 has been stabilized.

Example 5

The equipment X in FIG. 3 has one magnet 4, which is permanent. Magnet 4is placed around the nozzle system inlet 6 above the nozzle system 7.

The nozzle system 7 is composed of 3 channels placed radially towardsthe production pipe.

The equipment X is placed in the production pipe 10 centrically.

The liquid precursor Y is aqueous hydrogen peroxide solution with aconcentration of 80% by weight.

It enters the plasma-forming medium generator 5 and changes in it bychemical decomposition to the plasma-forming medium Z and this passesthrough the nozzle system inlet 6 into the nozzle system 7.

Plasma-forming medium Z is injected from the nozzle system 7 into thespace between two cylindrical electrodes, the upper electrode 1 and thelower electrode 2 under the effect of the ambient pressure of 50 MPa.Plasma-forming medium Z has a temperature of 500° C. and the propertiesof a mixture of supercritical water and supercritical oxygen.

The electric arc 3 is ignited by voltage ignition in a liquidenvironment between the upper electrode 1 and the lower electrode 2.Inter-electrode distance between the upper electrode 1 and the lowerelectrode 2 is maintained at a constant value of 1 mm after the electricarc 3 has been stabilized.

Example 6

The equipment X in FIG. 5 has one magnet 4, which is permanent. Magnet 4is placed under the nozzle system 7.

An upper dynamic flow restrictor 8 is placed on the outside of theequipment X, between the equipment and the production pipe 10, 10 mmabove the level of the nozzle system 7.

The nozzle system 7 is composed of 90 channels placed at an angle of 45°from the radial direction towards the production pipe 10. At the bottomof the equipment X, an electromagnet M is placed.

The equipment X is placed in the production pipe 10 centrically.

The liquid precursor Y is aqueous sodium hydroxide solution with aconcentration of 0.01% by weight.

It enters the plasma-forming medium generator 5 and changes in it byelectrochemical decomposition to the plasma-forming medium Z and thispasses through the nozzle system inlet 6 into the nozzle system 7.

Plasma-forming medium Z is injected from the nozzle system 7 into thespace between two cylindrical electrodes, the upper electrode 1 and thelower electrode 2 under the effect of the ambient pressure of 0.1 MPa.Plasma-forming medium Z has a temperature of 1° C. and the properties ofa mixture of water and oxygen.

The electric arc 3 is ignited by voltage ignition in a liquidenvironment between the upper electrode 1 and the lower electrode 2.Inter-electrode distance between the upper electrode 1 and the lowerelectrode 2 is maintained at a constant value of 4 mm after the electricarc 3 has been stabilized.

The broken material of the production pipe 10 is removed from thebreakdown point by hydrodynamic force generated by the flow of theplasma-forming medium Z acting on the broken particles. Subsequently,the particles of broken material (chips) are trapped by electromagnet Mat the bottom of the equipment X.

After the end of the process, the electric arc 3 is extinguished.Subsequently, the electromagnet M is switched off and trapped chips fallinto the bottom of the borehole. Subsequently, the equipment is pulledout from the production pipe 10 to the outside of the borehole.

Example 7

The equipment X has one magnet 4, which is electromagnet and is placedaround the nozzle system inlet 6 above the nozzle system 7.

An upper dynamic flow restrictor 8 is placed on the outside of theequipment X, between the equipment and the production pipe 10, at least10 mm above the level of the nozzle system 7.

A lower dynamic flow restrictor 9 is placed on the outside of theequipment X, between the equipment and the production pipe 10, at least10 mm under the level of the nozzle system 7.

The nozzle system 7 is composed of 48 channels placed at an angle of 80°from the radial direction towards the production pipe. The equipment Xis placed in the production pipe 10 centrically.

The liquid precursor Y is aqueous hydrogen peroxide solution with aconcentration of 1% by weight.

It enters the plasma-forming medium generator 5 and changes in it bythermal decomposition and electrochemical decomposition to theplasma-forming medium Z and this passes through the nozzle system inlet6 into the nozzle system 7.

Plasma-forming medium Z is injected from the nozzle system 7 into thespace between two cylindrical electrodes, the upper electrode 1 and thelower electrode 2 under the effect of the ambient pressure of 3 MPa.Plasma-forming medium Z has a temperature of 270° C. and the propertiesof a mixture of water vapour and oxygen.

The electric arc 3 is ignited by contact ignition in a liquidenvironment between the upper electrode 1 and the lower electrode 2.Inter-electrode distance between the upper electrode 1 and the lowerelectrode 2 is maintained at a constant value of 20 mm after theelectric arc 3 has been stabilized.

Example 8

The equipment X has one magnet 4, which is electromagnet and is placedaround the nozzle system inlet 6 above the nozzle system 7.

An upper dynamic flow restrictor 8 is placed on the outside of theequipment X, between the equipment and the production pipe 10, 10 mmabove the level of the nozzle system 7. A lower dynamic flow restrictor9 is placed on the outside of the equipment X, between the equipment andthe production pipe 10, 10 mm under the level of the nozzle system 7.

The nozzle system 7 is composed of 12 channels placed radially towardsthe production pipe. The equipment X is placed in the production pipe 10centrically.

The liquid precursor Y is water. Water enters the plasma-forming mediumgenerator 5 and changes in it by electrochemical decomposition to theplasma-forming medium Z and this passes through the nozzle system inlet6 into the nozzle system 7.

Plasma-forming medium Z is injected from the nozzle system 7 into thespace between two cylindrical electrodes, the upper electrode 1 and thelower electrode 2 under the effect of the ambient pressure of 25 MPa.Plasma-forming medium Z has a temperature of 50° C. and the propertiesof a mixture of water and supercritical oxygen.

The electric arc 3 is ignited by contact ignition in a liquidenvironment between the upper electrode 1 and the lower electrode 2.Inter-electrode distance between the upper electrode 1 and the lowerelectrode 2 is maintained at a constant value of 1 mm after the electricarc 3 has been stabilized.

Example 9

The equipment X has one magnet 4, which is permanent magnetelectromagnet and is placed around the nozzle system inlet 6 above thenozzle system 7.

An upper dynamic flow restrictor 8 is placed on the outside of theequipment X, between the equipment and the production pipe 10, 10 mmabove the level of the nozzle system 7.

The nozzle system 7 is composed of 60 channels placed radially towardsthe production pipe. The equipment X is placed in the production pipe 10centrically.

The liquid precursor Y is aqueous hydrogen peroxide solution with aconcentration of 10% by weight. It enters the plasma-forming mediumgenerator 5 and changes in it by thermal decomposition to theplasma-forming medium Z and this passes through the nozzle system inlet6 into the nozzle system 7.

Plasma-forming medium Z is injected from the nozzle system 7 into thespace between two cylindrical electrodes, the upper electrode 1 and thelower electrode 2 under the effect of the ambient pressure of 5.03 MPa.Plasma-forming medium Z has a temperature of 100° C. and the propertiesof a mixture of water and oxygen.

The electric arc 3 is ignited by voltage ignition in a liquidenvironment between the upper electrode 1 and the lower electrode 2.Inter-electrode distance between the upper electrode 1 and the lowerelectrode 2 is maintained at a constant value of 15 mm after theelectric arc 3 has been stabilized.

Example 10

The equipment X has two permanent magnets. An upper dynamic flowrestrictor 8 is placed on the outside of the equipment X, between theequipment and the production pipe 10 at least 10 mm above the level ofthe nozzle system 7.

The nozzle system is composed of 150 channels placed 90° from the radialdirection towards the production pipe. The equipment X is placed in theproduction pipe 10 centrically.

The liquid precursor Y is aqueous sodium hydroxide solution with aconcentration of 5% by weight. It enters the plasma-forming mediumgenerator 5 and changes in it by electrochemical decomposition to theplasma-forming medium Z and this passes through the nozzle system inlet6 into the nozzle system 7.

Plasma-forming medium Z is injected from the nozzle system 7 into thespace between two cylindrical electrodes, the upper electrode 1 and thelower electrode 2 under the effect of the ambient pressure of 60 MPa.Plasma-forming medium Z has a temperature of 374° C. and the propertiesof a mixture of supercritical water and supercritical oxygen.

The electric arc 3 is ignited by voltage ignition in a liquidenvironment between the upper electrode 1 and the lower electrode 2.Inter-electrode distance between the upper electrode 1 and the lowerelectrode 2 is maintained at a constant value of 0.1 mm after theelectric arc 3 has been stabilized.

Example 11

The equipment X has two magnets 4, and both magnets are permanentmagnets.

The nozzle system is composed of 18 channels placed 1° from the radialdirection towards the production pipe. The equipment X is placed in theproduction pipe eccentrically.

The liquid precursor Y is aqueous hydrogen peroxide solution with aconcentration of 90% by weight.

It enters the plasma-forming medium generator 5 and changes in it bychemical decomposition to the plasma-forming medium Z and this passesthrough the nozzle system inlet 6 into the nozzle system 7.

Plasma-forming medium Z is injected from the nozzle system 7 into thespace between two cylindrical electrodes, the upper electrode 1 and thelower electrode 2 under the effect of the ambient pressure of 22.06 MPa.Plasma-forming medium Z has a temperature of 1000° C. and the propertiesof supercritical water and supercritical oxygen.

The electric arc 3 is ignited by voltage ignition in a liquidenvironment between the upper electrode 1 and the lower electrode 2.Inter-electrode distance between the upper electrode 1 and the lowerelectrode 2 is maintained at a constant value of 2 mm after the electricarc 3 has been stabilized.

INDUSTRIAL APPLICABILITY

The equipment for removing the production pipe in the borehole andmethod for removing the production pipe in the borehole of thisinvention is utilised in the mining industry, particularly in thepetroleum industry when performing decommissioning operations.

LIST OF REFERENCE SIGNS

-   1—Upper electrode-   2—Lower electrode-   3—Electric arc-   4—Magnet-   5—Plasma-forming medium generator-   6—Nozzle system inlet-   7—Nozzle system-   8—Upper dynamic flow restrictor-   9—Lower dynamic flow restrictor-   10—Production pipe-   11—Liquid precursor supply-   12—Electrical power supply-   13—Coolant supply-   14—Data cable-   15—Control unit-   16—First electrode of the generator-   17—Second electrode of the generator-   18—Generator chamber-   X—Equipment for removing the production pipe-   Y—Liquid precursor-   Z—Plasma-forming medium-   M—Electromagnet to collect particles of the degraded material-   C—Centralizer

1. An apparatus for disintegrating a production pipe (10) in a borehole,the apparatus mechanically connected by means of a Bottom Hole Assemblyto an electrical power supply (12), coolant supply (13), data cable (14)and control unit (15), wherein the apparatus contains equipment (X)which is placed inside the production pipe (10) without any contact tothe production pipe (10), while the equipment (X) is connected to aliquid precursor supply (11), wherein the liquid precursor supply (11)enters a generator (5) of plasma-forming media connected to a nozzlesystem inlet (6), wherein the nozzle system inlet (6) is connected to anozzle system (7) which is placed in a space between two cylindricalmechanically movable electrodes comprising an upper electrode (1) and alower electrode (2), wherein the upper electrode (1) and the lowerelectrode (2) are placed axially with respect to each other around thecircumference of the equipment (X) and coaxially placed towards theproduction pipe (10), wherein, while in the axis of the upper electrode(1) and the lower electrode (2), at least one magnet (4) is placedaround the nozzle system inlet (6), wherein the magnet (4) is positionedabove the nozzle system (7) and/or under the nozzle system (7).
 2. Theapparatus for disintegrating the production pipe in the borehole ofclaim 1 wherein one or more centralizers (C) are placed on the outsideof the equipment (X), which are in a mechanical contact with theproduction pipe (10).
 3. The apparatus for disintegrating the productionpipe in the borehole of claim 1 wherein the generator (5) of theplasma-forming media consists of one or several interconnected chambers(18), each chamber (18) having at least one inlet and one outlet, and atleast one chamber (18) contains at least one pair of electrodes, a firstelectrode (16) of the generator being at a negative electrical potentialand a second electrode (17) of the generator being at a positiveelectrical potential.
 4. The apparatus for disintegrating the productionpipe in the borehole of claim 1 wherein the magnet (4) is a permanentmagnet or electromagnet.
 5. The apparatus for disintegrating theproduction pipe in the borehole of claim 1 wherein the nozzle system (7)is composed of 3-150 channels placed radially towards the productionpipe (10) or at an angle of 1-90° from the radial direction.
 6. Theapparatus for disintegrating the production pipe in the borehole ofclaim 1 wherein the equipment (X) and all parts of the equipment (X) areadapted to the effect of pressure in a range of 0.1-70 MPa.
 7. Theapparatus for disintegrating the production pipe in the borehole ofclaim 1 wherein an upper dynamic flow restrictor (8) is placed on theoutside of the equipment (X), between the equipment (X) and theproduction pipe (10), and at least 10 mm above the level of the nozzlesystem (7).
 8. The apparatus for disintegrating the production pipe inthe borehole of claim 1 wherein a lower dynamic flow restrictor (9) isplaced on the outside of the equipment (X), between the equipment (X)and the production pipe (10), and at least 10 mm under the level of thenozzle system (7).
 9. The apparatus for disintegrating the productionpipe in the borehole of claim 1 wherein an electromagnet (M) is placedat the bottom of the equipment (X).
 10. The apparatus for disintegratingthe production pipe in the borehole of claim 1 wherein the equipment (X)is placed in the production pipe (10) eccentrically.
 11. A method fordisintegration of the production pipe in the borehole by means of theapparatus of claim 1 wherein the equipment (X) is inserted into theproduction pipe (10) in the borehole and a liquid precursor (Y) issupplied through the liquid precursor inlet (11) to the generator (5) ofplasma-forming media, which changes the liquid precursor (Y) to theplasma-forming medium (Z), wherein the plasma-forming medium (Z) passesthrough the nozzle system inlet (6) into the nozzle system (7) and isinjected from the nozzle system (7) into the space between the twocylindrical mechanically movable electrodes, the upper electrode (1) andthe lower electrode (2), wherein a liquid environment is providedbetween the upper electrode (1) and the lower electrode (2) thatcomprises a pressure in a range of 0.1-70 MPa and the temperature of theplasma-forming media (Z) maintained at a range of 1-1000° C., wherein anelectric arc (3) is created in the space between the two cylindricalmechanically movable electrodes with an input power in a range of10-10000 kW, and the electric arc (3) is ignited either by contactignition or by voltage ignition, wherein the electric arc (3) is evenlyrotated on a circle by the magnetic field of the magnet (4) and/or byinteraction of the electric arc (3) with the flow of the plasma-formingmedia (Z), an axis of the rotational movement of the electric arc (3)being identical to an axis of symmetry of the upper electrode (1) andthe lower electrode (2), and wherein the production pipe (10) isdegraded by heat flow produced by rotating the electric arc (3) and theplasma-forming media (Z), subsequently broken material is separated fromthe production pipe (10) and is removed from a breakdown point, and thenthe electric arc (3) is extinguished and the equipment (X) is pulled outfrom the production pipe (10) to the outside of the borehole.
 12. Themethod for disintegration of the production pipe in the borehole ofclaim 11 wherein the generator (5) of the plasma-forming media changesthe liquid precursor (Y) to the plasma-forming medium (Z) by thermaldecomposition, electrochemical decomposition, chemical decomposition, ora combination of at least two of these decompositions.
 13. The methodfor disintegration of the production pipe in the borehole of claim 11wherein for pressures from 22.06 to 70 MPa and temperatures 374-1000°C., the plasma-forming medium (Z) has properties of a mixture ofsupercritical water and supercritical oxygen.
 14. The method fordisintegration of the production pipe in the borehole of claim 11wherein for pressures from 5.04 to 22.05 MPa, the plasma-forming medium(Z) has properties of a mixture of water and supercritical oxygen, or amixture of water vapour and supercritical oxygen.
 15. The method fordisintegration of the production pipe in the borehole of claim 11wherein for pressures from 0.1 to 5.03 MPa, the plasma-forming medium(Z) has properties of water enriched by oxygen, or a mixture of watervapour and oxygen.
 16. The method for disintegration of the productionpipe in the borehole of claim 11 wherein liquid precursor (Y) is water,a mixture of ethanol and water in any ratio, or a mixture of water andhydrogen peroxide in any ratio, or an aqueous alkali metal hydroxidesolution with a concentration of 0.01-5% by weight.
 17. The method fordisintegration of the production pipe in the borehole of claim 11wherein after ignition the electric arc (3) by deflecting the electrodes(1) and (2) in the axial direction, an arc channel is elongated to thelength of 0.1 to 20 mm, whereby an inter-electrode distance between theupper electrode (1) and the lower electrode (2) is maintained at aconstant value selected from an interval of 0.1-20 mm after the electricarc (3) has been stabilized.
 18. The method for disintegration of theproduction pipe in the borehole of claim 11 wherein the particles of thebroken material of the production pipe (10) are trapped by electromagnet(M) at the bottom of the equipment (X).
 19. The method fordisintegration of the production pipe in the borehole of claim 18wherein after the end of the production pipe (10) breakdown process, theelectromagnet (M) is switched off and trapped particles of desintegratedmaterial of the production pipe (10) fall into the bottom of theborehole.
 20. The method for disintegration of the production pipe inthe borehole of claim 19 wherein the disintegrated material of theproduction pipe (10) is removed from the breakdown point by hydrodynamicforces generated by the flow of the plasma-forming media (Z), coolant(13), a mud, or gravitational force.